James (James McAvoy) is a British agent under the cover of a water engineer, while Danny (Alicia Vikander) is a bio-mathematician working on a deep-sea diving project to explore the origin of life on our planet. On a chance encounter in a remote resort in Normandy where they both prepare for their respective missions, they fall rapidly, and unexpectedly, into each other's arms and a deliriously wild love affair develops, even though their jobs are destined to separate them. Danny sets off on a perilous quest to dive to the bottom of the ocean. James's assignment takes him to Somalia, where he is sucked into a geopolitical vortex that puts him in grave danger. Both characters are subject to different kinds of isolation as they pine for each other; their determination to reconnect becomes as much an existential journey as a love story.